The present invention relates to the field of processes for manufacturing particles coated with an activated lignosulfonate, and, more particularly, to the field of processes for manufacturing particles coated with an activated lignosulfonate for use in filters
Water may contain many different kinds of contaminants including, for example, particulates, harmful chemicals, and microbiological organisms, such as bacteria, parasites, protozoa and viruses. In a variety of circumstances, these contaminants must be removed before the water can be used. For example, in many medical applications and in the manufacture of certain electronic components, extremely pure water is required. As a more common example, any harmful contaminants must be removed from water before it is potable, i.e., fit to consume. Despite modern water purification means, the general population is at risk, and in particular infants and persons with compromised immune systems are at considerable risk.
In the U.S. and other developed countries, municipally treated water typically includes one or more of the following impurities: suspended solids, bacteria, parasites, viruses, organic matter, heavy metals, and chlorine. Breakdown and other problems with water treatment systems sometimes lead to incomplete removal of bacteria and viruses. In other countries, there are deadly consequences associated with exposure to contaminated water, as some of them have increasing population densities, increasingly scarce water resources, and no water treatment utilities. It is common for sources of drinking water to be in close proximity to human and animal waste, such that microbiological contamination is a major health concern. As a result of waterborne microbiological contamination, an estimated six million people die each year, half of which are children under 5 years of age.
In 1987, the U.S. Environmental Protection Agency (EPA) introduced the xe2x80x9cGuide Standard and Protocol for Testing Microbiological Water Purifiersxe2x80x9d. The protocol establishes minimum requirements regarding the performance of drinking water treatment systems that are designed to reduce specific health related contaminants in public or private water supplies. The requirements are that the effluent from a water supply source exhibits 99.99% (or equivalently, 4 log) removal of viruses and 99.9999% (or equivalently, 6 log) removal of bacteria against a challenge. Under the EPA protocol, in the case of viruses, the influent concentration should be 1xc3x97107 viruses per liter, and in the case of bacteria, the influent concentration should be 1xc3x97108 bacteria per liter. Because of the prevalence of Escherichia coli (E. coli, bacterium) in water supplies, and the risks associated with its consumption, this microorganism is used as the bacterium in the majority of studies. Similarly, the MS-2 bacteriophage (or simply, MS-2 phage) is typically used as the representative microorganism for virus removal because its size and shape (i.e., about 26 nm and icosahedral) are similar to many viruses. Thus, a filter""s ability to remove MS-2 bacteriophage demonstrates its ability to remove other viruses.
Due to these requirements and a general interest in improving the quality of potable water, there is a continuing desire to provide processes for manufacturing low cost filter materials, which are capable of removing bacteria and/or viruses from a fluid. Further, there is a continuing desire to provide processes for manufacturing such filter materials in the form of fibers in order to reduce the pressure differential needed to pass a fluid through the filter material.
Processes for forming a filter material are provided. A preferred process includes the steps of coating a filter particle with a lignosulfonate, carbonizing the coating, and activating the coating. Preferred lignosulfonates include ammonium lignosulfonate and zinc lignosulfonate. The coating can be applied to a variety of filter particles, including fibers, granules, and screens.